Process for coating a web surface with a plurality of emulsion coating layers

ABSTRACT

A method for the production of webs coated with several emulsions, comprising coating and drying means arranged in succession, in the latter being connected to air supply and discharge shafts. A plurality of coating means are arranged at a selectable spacing from one another along the web which is guided in loop formation, the physical parameters for coating and drying are adjustable for each layer.

United States. Patent 1191 Herzhoff et a1.

[ PROCESS FOR COATING A WEB SURFACE WITH A PLURALITY OFEMULSION COATING LAYERS AGFA-Gevaert Aktiengesellschaft, Leverkusen, Germany Filed: Oct. 4, 1970 Appl. No.: 95,210

Assignee:

[30] Foreign Application Priority Data Dec. 11, 1969 Germany 1962089 US. Cl 117/34, 34/23, 34/155, 117/119,117/119.8,l17/152,118/61,118/65 Int. Cl G03c l/74, B44d 1/14, 844d l/48 Field of Search 117/119.8, 34,119, 152; 118/67, 65, 61; 34/12, 23,155, 212

1451 Feb. 19, 1974 [56] References Cited UNITED STATES PATENTS 2,834,993 5/1958 Dipner 117/l19.8 X 1,560,579 11/1925 Jones 34/156 UX 1,591,102 7/1926 Randolp 118/67 X 1,772,081 8/1930 Hochste tter 118/67 X 1,979,346 11/1934 Rappolt et al. 34/23 2,597,999 5/1952 Knopp 3,311,499 3/1967 Busch et al.. 3,362,079 1/1968 Fleissner 3,508,947 4/1970 Hughes 929,651 8/1909 Bayne et a1. 117/119.8 X

Primary Examiner-Alfred L. Leavitt Assistant Examiner-Thomas E. Bokan Attorney, Agent, or Firm-Connolly and Hutz [57] ABSTRACT A method for the production-of webs coated with several emulsions, comprising coating and drying means arranged in succession, in the latter being connected to air supply and discharge shafts. A plurality of coating means are arranged at a selectable spacing from one another along the web which is guided in loop formation, the physical parameters for coating and drying are adjustable for each layer.

9 Claims, 7 Drawing Figures L, n 4 11 7 11 12 u 15 D g n "13 n a]? n 1 19 11 [1 ll D I U n 3 11 PATENTEUFEB 191974 SHEET 2 [1F 5 mama] r n- 1914 i 3, 793 051 f SHEET 3 BF 5 FIG. 3

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PROCESS FOR COATING A WEB SURFACE WITH A PLURALITY OF EMULSION COATING LAYERS This invention relates to a means for producing webs with a multiple coating of photographic emulsions. In such a case, coating and drying means are arranged alternately in succession, the drying means consisting of air supply and discharge shafts.

Coating plants having two coating arrangements are already known. In these known arrangements, the film web is guided from the first coating arrangement through a solidifying section to the next coating arrangement and then through a solidifying section into a drier. The emulsion is prepared in a melting chamber and flows to the coating arrangements. The section of the plant comprising the coating arrangements and the solidifying sections is generally known as the coating machine. The construction of the coating machine is determined by the requirement that the web should be guided without any contact of the coated side with rollers from the first to the second coating arrangement. It is because of this requirement that helical web guiding means is for example provided as is known. Suspension or channel driers as driers for coating plants are known. The drying air is conducted by a circulated air system, in which the air is always circulated in the same drying section, or in a helical system, in which the air is always conducted on to the next following section.

A more recent development consists in coating several layers without intermediate drying in a single multi-layer coating device. Multi-layer coating devices are known which can easilybe incorporated into a conventional coating plant.

However, this known process also has disadvantages. The ratio between thethicknesses of the layers which are simultaneously to be applied can only be freelyselected within limits and it is dependent on the viscosity and wetting ratios.

Usually, the multi-layer emulsion web preformed by means of the coating arrangement is stretched on being transferred to the support. Therefore, the spinnability of the emulsions is-to be taken into account.

Consequently, in view of the coating operation, it is frequently necessary to provide the coating solutions with additives which influence their flow behaviour, in order to obtain satisfactory casting qualities of the separate layers.

Such additives often impair the technological properties of the products and, at best only mean a restriction of the manipulation latitude for producing extremely constant and thin layers at high working speeds.

Often different coating systems are suitable for the separate layers. It should therefore be possible individually to select the coating system.

Each separate layer sets different requirements as regards the desired physical conditions existing during the drying. The essential variables of state, such as temperature, moisture content and flow velocity of the air,- and also the drying time for the respectively required residual water content, should therefore be freely selectable for each layer if it is desired to produce optimum technological properties and highest output of the plant. It should thus be possible to use individual coating systems for the application of the separate layers.

The object as described above is achieved according to the invention, in connection with an arrangement having coating and drying means arranged in succession, comprising a plurality of coating means arranged at a variable spacing from one another along the web guided in loop formation, the physical parameters important for the coating and drying being adjustable on each coating and drying means for each layer. As coating means, types of casting units of the same or different types can be used,.such as air brush or extruder casting units.

According to a preferred embodiment of the invention, the air discharge shafts of a drying means respectively open into a return air duct, and this duct, for the production of different air paths, is connected through adjustable and closable flaps to a ventilator mixing chamber belonging to the respective section and such a chamber belonging to the next section, and to a moist air duct which is common to all drying means. The return air duct is advantageously connected by way of adjustable and closable flaps or dampers to a bypass duct which is common to all drying means, the latter duct being capable of subdivision by partitions, while each mixing chamber is in its turn connected by way of adjustable and closable flaps or dampers to the drying air duct and by-pass duct.

In order to be able to dry the coated web in a drying means successively at different temperatures, the air supply shaft is subdivided into at least two ducts which can be separately heated and which communicate in the different sections of the drying means with a set of slit nozzles. t

The plant preferably consists of at least two similar structural elements, which respectively comprise that portion of the machine frame for guiding the web, the drying means and the drying air supply and also space for a coating means and the associated emulsion preparation stage. The construction readily allows a certain freedom in the choice of the drying time necessary for a coated web element. If in fact the coating means is omitted at the place provided for it between two drying means and is replaced by a simple guide arrangement or if the web travels through an existing coating means without being coated, the drying time is doubled. By

' appropriate choice of the location for a coating means,

it thus becomes possible for the separate layers to be dried for different drying times.

The mixing chambers are advantageously so arranged that their partitionwalls are offset from the partition walls of adjoining return air ducts by the length of half a mixing chamber.

The air supply and discharge shafts of a drying means are arranged in a common housing which is subdivided by partitions and formed with openings towards the web, a machine frame for guiding the web always being arranged between two of these housings. The machine frame for guiding the web is formed as a suction shaft. The suction shaft is provided towards the adjoining housings with web-guiding rollers, and respectively two web-guiding rollers form a two-roller hollow forming suction unit. Openings for discharging the air drawn in by the said suction unit are arranged in the walls of the suction shaft after the web-guiding rollers.

A particularly good guiding action for the web in the vicinity of a coating means is obtained by a hollowforming suction unit extending directly up to the casting roller of the coating means and provided with a plurality of guide rollers arranged in parallel disposed at the bottom end of the suction shaft. In this way, webs 3. of a nature which cannot be unwound without tension exactly into one plane are guided in the region of the coating roller without any formation of creases or deformation. For a satisfactory coating operation, the web should lie uniformly everywhere on the casting roller.

The drying means according to the invention are not restricted in their use to the coating arrangement which has been described. They can in principle be used in all those cases where an intermediate drying is necessary with application of several layers.

Asregards the drying, the advantages which are produced by the invention consist more especially in that the drying characteristic for the individual layers can be chosen in the best possible manner. A circulating air or helical system is possible. Due to the by-pass duct, the possibility also exists of by-passing one or more drying sections. v I

The advantages produced .by the invention consist more especially in that the drying conditions for the separate layers can be chosen in optimum manner. Because of the bypass duct, it is also possible for one or more drying sections to be by-passed.

By the arrangement of the ducts and air shafts according to the invention, complicated pipe conduit systems for the conduction of drying air are avoided, since the airchamber system is repeated in each section and the necessary flaps or shutters arearranged in the partitions.

One embodiment of the invention is to be more fully described by way of example and by reference to drawings, wherein: i

FIG. 1 is a perspective view in section through the coating and drying plant, from which the guiding of the web can be more clearly seen.

FIG. 2 is a perspective view insection through the coating and drying plant, from which the path of the air can be seen, and I FIGS. 3 to 7 are block diagrams for different possibilities as regards the path of the drying air.

In FIG. I, a film or paper web 1, coming from an unwinding arrangement which is not shown, is guided in vertical loops through the coating and drying plant and then is conveyed to a winding arrangement, which also is not shown.

Arranged at each second base point of the loops is a coating means -2.

In the straight sections of the loops, the web is guided over two-roller hollow-forming suction units 3, in order to avoid turning over of the edges. The guiding of the layer side at the upper end of the loops is effected by five drying means disposed side-by-side. The drying air produced in an air-preparing plant is supplied by way of a drying air header duct T to the drying means. The air, enriched. with water, is wholly or partially discharged through a moist air header duct F, depending on the circuit arrangement. In addition, a by-pass duct U is provided (this only being shown in FIGS. 6 and 7). Shut-off members, fans, heaters and the like are not shown, so as not to complicate-the drawings.

FIG. 3 shows the drying means n to q in a so-called circulated air system. The air-quantity l is supplied to each duct. One quarter of the moistened air is discharged into the moist air header duct F, while three quarters remain in circulation and one quarter is made up from the dry air header duct T.

FIG. 4 shows the same drying means with a so-called helical system. The air quantity 1 taken from the duct T is sent successively through the sections it to q and,

after having suitably absorbed moisture, is delivered into the duct F.

According to FIGS. 5 and 6, altogether only a quarter of the quantity of air circulated in each drying section is supplied-to the drying means n to q. The dry air in this case is supplied before the section It and the moist air is discharged after the section q;

According to FIG. 5, always one quarter of the circulated air quantity is carried forward to the next drying section by means of a combined circulation and helical system.'

On the contrary, according to FIG. 6, the strictly helical system as in FIG 4 is retained and three quarters of the circulated air quantity is fed back from section q by way of the by-pass duct U to the section n.

FIG. 7 shows a system for the drying means m to q, inwhich the full air quantity is first of all supplied to the last section q and then through the by-pass duct U to the first section m. From the latter, the air is carried on in helical'system as far as the section p. This system is frequently used when the properties of the material being dried at the end and commencement of the drying section requires a drying air with a low wet bulb temperature, but higher temperatures of the material are permissible in the middle,.-

The systems which are shown in the diagrammatic FIGS. 3 to 7 can be combined in any arbitrary manner with a coating plant having a relatively large number means of curved hollow-forming suction units 4. Suction units 5 are also arranged in the vicinity of the coating means in order to produce a good support of the web on the casting roller, also with low-rigidity webs.

The diagrams in FIGS. 3 to 7 show various possibilities as regards the path or guiding of the drying air.

of drying means, corresponding to the requirements of the drying operation.

The air passages belonging to the separate systems are to be seen from FIGS. 1 and 2.

When operating with circulated air according to FIG. 3 in any drying section, a fan 8 blows the drying air through heater elements 9 and filters 10 and through the supply air ducts 11 into the nozzle ducts 12 in the housing 7 of the drying means. The air is blown through slit nozzles 13 on to the web 1 which is to be dried and discharges laterally over the edges of the web. The supply air path is symmetrically divided behind the heater element into two ducts. By this means, it is possible for the film web to have air blown thereon at different temperatures in different sections of the drying means. Most of the return air is drawn by suction through slots 14 into air discharge shafts 15 arranged laterally of the nozzle duct 12 and passes .through the duct 16 into the return air duct 17. t

A small part of the return air is drawn through the two-roller hollow-forming suction unit 3 and the curved suction unit 4 from the drying chamber and supplied through ducts l8 and 19 and fans 20 and 2], which produce the negative pressures necessary in the suction units, to the return air duct 17.

A small part of the total return air is removed from the cycle and conveyed through a damper 22 into the moist air header duct F. The remainder flows again through a damper 23 to the fan 8 arranged at the bottom of a mixing chamber 24. A portion corresponding to the discharged moist airquantity is removed by way of another damper 25 from the dry air header duct T and admixed in the mixing chamber 24 with the circulated air cycle. Dampers 26 and 27 remain closed when operating with circulated air.

With a helical air system according to FIGS. 4 to 7, the exhaust air is wholly or partially conveyed by way of the damper 26 to the fan of the adjacent chamber.

When using the by-pass duct U according to FIGS. 6 and 7, the latter is connected by way of dampers 28 to the required air duct and by way of dampers 27 to the required mixing chamber. Depending on its length, the by-pass duct U can be subdivided by partitions 29 (FIG. 2), so that it can be used simultaneously for several air cycles.

As regards construction, the arrangement of the air passages in the upper part of the dry air duct (see FIG. 2) is advantageous. In this Figure, the important air chambers, such as the fan mixing chamber 24, return air duct 17, moist air header duct F, drying air header duct T, by-pass duct U, are constructed as a unit which is repeated in each structural element, and in the partitions of which are arranged the connecting dampers necessary for producing the different air circulation systems.

With the construction described here, the three ducts F, U and T run parallel to one another and have common partitions. The ducts F, U and T are preferably so disposed above the mixing chambers 24 that they pass through all mixing chambers. The return air ducts 17 respectively open vertically into the duct system F, U. The partitions 30 of adjoining mixing chambers 24 are offset relatively to the partitions 31 of adjoining return air ducts 17 by half the length L of a mixing chamber, so that some of the return air from the return air duct 17 can be directed throughthe corresponding dampers directly into two mixing chambers 24 which follow one another.

By means of this arrangement of the duct system and the mixing chambers, the aforementioned air circulation systems according to FIGS. 3 to 7 can be achieved with shortest possible air passages.

We claim:

l. A process for coating one of the two surfaces of an elongated web with a plurality of emulsion coating layers comprising the steps of disposing the web in a path having a number of substantially parallel open loops having elongated substantially straight paths and relatively short curved end paths with spaces inbetween the substantially elongated straight paths, applying coat- 4 air applied within the loops is at least partially interings to the web at the end paths at one side of the loops for maintaining the coatings on one surface of the web and inbetween alternate loops whereby the web surfaces within successive loops are coated and uncoated, supporting the loops at spaced supporting surfaces within the alternate loops of uncoated web surfaces to permit the web to be supported without structural contact upon its coated surface, conveying the web in the path in contact with the spaced supporting surfaces, discharging drying air against the web inbetween the loops having coated websurfaces and withdrawing a portion of the drying air through the spaced supporting surfaces within the loops having uncoated web surfaces whereby the web is maintained in firm supporting contact against the spaced supporting surfaces by the resultant differential pressure as the coatings are dried by the discharged drying air, withdrawing most of the discharged drying air from between the loops of coated web surfaces substantially adjacent its area of discharge to prevent the discharged drying air at one loop from interfering with that discharged at another, and controlling the drying characteristics of the air discharged within the loops of coated web surfaces to obtain predetermined drying characteristics for the applied coatings within each of the loops having coated web surfaces.

2. A process as set forth in claim I where in the discharged drying air is separated into two separate drying sections within each of the loops of coated web surfaces with each straight portion of the loop of coated web surfaces comprising a separate drying section to thus provide two separate drying sections within a loop of coated web surfaces.

3. -A process as set forth in claim 2, wherein no coating is applied upon at least one end path at the side of the loops at which the coatings are applied whereby an applied coating is dried within two loops having coated web surfaces and thus by air discharged in four separate drying sections.

4. A process as set forth in claim 1 wherein the drying mixed with air discharged in different loops.

5. A process as set forth in claim 1 wherein the path is vertically disposed to dispose the ends of the loops at the side of the loops at which the coatings are applied at a common level thereby facilitating installation and operation.

6. A process as set forth in claim 5 wherein the common level is at the base point of the loops and the coatings are applied at the bottom base ends of the loops.

7. A process as set forth in claim 1 wherein portions of the drying air are partially newly provided and partially recirculated.

8 A process as set forth in claim 1 wherein the spaced supporting surfaces are substantially distantly spaced from each other.

9. A process as set forth in claim I wherein each coating is substantially dried before the next coating is applied.

"*nrqrm STATES PATENT own:

CERTIFICATE OF CORRECTION Patent No. 3-793-O51 Dated February 10 1971: nwemms F t3;.-l E.rzhQf. Hans Greg wolf n Sghwpir-hpr 14m 11. is certified that error appears in the above-idontif ed paten and that said Letters Patent are hereby corrected as shown below:

; Cha-h'gethe filing date of "Oc tober 4, 1970" to Decembe r 4 1970 Change the invent tor s name "Hans Gree" .to

-- Hans Gref --j.

Signed an d sealed this 29th day of October 1974.

(SEAL) Attestz McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner pf Patents Fi'enken, Karl Voss, Stephan Platz', Gunther Koe ke, Seer Bramiger 

2. A process as set forth in claim 1 where in the discharged drying air is separated into two separate drying sections within each of the loops of coated web surfaces with each straight portion of the loop of coated web surfaces comprising a separate drying section to thus provide two separate drying sections within a loop of coated web surfaces.
 3. A process as set forth in claim 2, wherein no coating is applied upon at least one end path at the side of the loops at which the coatings are applied wheReby an applied coating is dried within two loops having coated web surfaces and thus by air discharged in four separate drying sections.
 4. A process as set forth in claim 1 wherein the drying air applied within the loops is at least partially intermixed with air discharged in different loops.
 5. A process as set forth in claim 1 wherein the path is vertically disposed to dispose the ends of the loops at the side of the loops at which the coatings are applied at a common level thereby facilitating installation and operation.
 6. A process as set forth in claim 5 wherein the common level is at the base point of the loops and the coatings are applied at the bottom base ends of the loops.
 7. A process as set forth in claim 1 wherein portions of the drying air are partially newly provided and partially recirculated.
 8. A process as set forth in claim 1 wherein the spaced supporting surfaces are substantially distantly spaced from each other.
 9. A process as set forth in claim 1 wherein each coating is substantially dried before the next coating is applied. 